Mechanical, abrasive processing methods are used predominantly at the present time for the pretreatment of workpieces of composite fiber materials, which are to be joined together by gluing. However, such mechanical methods require a relatively high degree of control, in order to ensure the required reproducibility of the surface quality of the workpieces to be joined. The surface quality alone guarantees the optimum adhesion of the gluing. On the other hand, it cannot be reasonably assumed with such a mechanical pretreatment that the strength properties of the work pieces, so pretreated, will remain unaffected.
Another possibility for achieving the residue-free, reproducible surface required for gluing may under some circumstances be provided by the removal, immediately before the gluing step, of the fragmented tissue that is still present. This method, however, is not universally usable and its reliability must therefore be demonstrated anew for each combination of composite fiber material and adhesive. Particularly in the case of composite fiber material with improved strength properties, this method frequently, moreover leads to unsatisfactory results.
Finally, attempts have been made to employ wet chemistry pretreatment methods of the type mentioned at the beginning. Up until now, these methods have been either comparatively unsuccessful or their introduction into the production process has been opposed, as in the case of a use of chromic acid, by industrial hygiene and environmental points of view.